1. Field of the Invention
This invention relates to the field of ophthalmic optics and artificial lens adapted to be affixed to an eye and more specifically relates to an artificial lens adapted to be located in an eye having a macula wherein the artificial lens comprises a multifocal optical lens system wherein each principal axis is eccentric to each other for directing light rays from each image of each lens onto the macula of an eye. In the preferred embodiment a first lens system having a prism directs paracentral light rays from a near object onto the macula and a second lens system having a prism positioned in a cooperating relationship to the first lens system directs central light rays from a distant object onto the macula of an eye.
This invention also relates to method for producing multiple images of an object for an eye using a multifocal optical lens system wherein the principal axis of each lens system is eccentric to each other.
2. Description of the Prior Art
It is known in the art that when the optical power of the natural eye is emmetropic, the eye is naturally focused for distance with the ciliary body at rest. The natural eye has the ability to change (increase or decrease) the converging power of the natural (crystalline) lens for near vision and for intermediate vision, that is vision in the range of about 10" to about 18" or 20".
With aging, the eye's natural (crystalline) lens loses its ability to adequately increase its converging power. In order to provide for a sharp focus near vision, it is known in the art to make use of artificial lens system. It is also known in the art to utilize a plurality of artificial lens systems such as glasses or spectacles, contact lens, intraocular lens, corneal lens and intracorneal lens, all of which are utilized to produce a focused near vision. Such lens systems are designed to use concentric lens system for distant and near images and the images are passed through the natural round pupil as the only entrance of light to the retina.
Glasses and spectacles are well known in the art and are selected to have a diopter power to produce the correction required to focus near vision. Also, it is known in the art that such glasses or spectacles comprise bifocal lens for near and distant vision correction or trifocal glasses for near, intermediate and distant correction vision, all of which have concentric principal axes.
Contact lens likewise are well known in the art. Typical of the known prior art which describes contact lens are U.S. Pat. No. 3,034,403 relating to a contact lens of apparent variable light absorption characteristics; U.S. Pat. No. 3,270,099 which relates to a method for making multi-focal length, concentric contact lens and U.S. Pat. No. 4,402,579 which discloses and teaches various concentric axes contact lens structures.
Typically, contact lens are positioned over the anterior surface of the pupil. The natural crystalline lens and iris remain in place and perform their natural functions and cooperate with the contact lens to focus the appropriate images on the macula.
It is also known in the art to utilize prisms in glasses and spectacles both located along the same axis to improve the image focused on the natural crystalline lens.
It is also known in the art to utilize intraocular lens to replace the natural crystalline lens in a cataracts operation. Intraocular lens are implanted into either the anterior chamber or posterior chamber of the eye and are utilized in place of the natural crystalline lens. Typical of such intraocular lens are U.S. Pat. No. 4,010,496 which discloses a bifocal lens which is positioned within the anterior chamber; U.S. Pat. No. 4,244,060 which discloses an intraocular lens having a lens body and a plurality of lens-centering filaments extending outwardly in a common plane from spaced rim portions of the lens body; U.S. Pat. No. 4,485,499 which discloses intraocular posterior chamber lens and U.S. Pat. No. 4,976,732 which discloses an optical lens wherein the lens body has integral therewith a predetermined area which is adapted to selectively intercept and pass light through the lens body in a manner to obtain an optical effect for substitution of the loss of accommodation of a phakic, aphakic and pseudophakic eye.
U.S. Pat. No. 4,994,080 discloses an optical lens having stenopaeic openings located in the central area thereof which produces parallel light transmitting paths for passing light rays along a path defining the visual axis of the eye and forwarded onto the fovea centralis in a manner to obtain an optical effect by increasing the depth of focus of the eye in order to substitute for the loss of at least one of the focusing power and the accommodation of the eye.
Artificial lens are also known in the art which are capable of being implanted into the cornea of an eye and which become encapsulated by growth of the corneal epithelium of the cornea of the eye over the anterior surface of lens implanting the same. One such artificial lens fabricated from a collagen-hydrogel material is disclosed in U.S. Pat. No. 5,112,350.
The natural (crystalline) lens degrades as the age of an individual approaches the 40-to-50-year-age range such that the natural lens can no longer adequately change shape due to a loss of elasticity of the lens of the eye causing defective accommodation and inability to focus sharply for near vision. This condition is referred to as a presbyopia.
When this occurs, an individual requires additional converging power (plus) for near vision. This is commonly supplied by the lower lens in a bifocal artificial lens. As the individual approaches the age range of 65-to-70-years, substantially all of the natural converging powers of the lens is lost and additional convergence for near requirement must be made stronger. In such instances, the bifocal lens of the glasses, contact lens or artificial lens must supply all the convergence of light for near vision.
Following cataract extraction and intraocular lens implantation, there remains the need for additional convergence of light for near vision. With monofocal intraocular lens ("IOL") focused for distance, the near vision convergence must be completely supplied by the bifocal glasses or a single vision reading glasses.
Multiple lens IOLs are known in the art and typically create multiple light rays which are directed on the macula. The artificial lens disclosed in U.S. Pat. Nos. 3,034,403 and 4,976,732 described above produce multiple light rays for the eye. Typically, the multiple lens IOLs do not have provisions for restricting the light from near and far and spontaneously flood the macula with excess light. Also, light passing through multiple lens IOLs enters the eye through each of the optical systems resulting in both a sharp image and a blurred image of the same image impinging upon the macula. This results in: (a) loss of color purity; (b) loss of contrast; and (c) inability of the retina to adapt since the brain perceives the flooding and receipt of extraneous light as too much light.
An intraocular lens that functions as a regular intraocular lens and, in tandem with or concentric with a high plus spectacle lens, as a Galilean telescope, was described in an article entitled "The Telescopic Intraocular Lens" by Jeffrey Koziol, M.D., which appeared at pages 43 and 44 of a compilation of papers presented at the Eleventh National Science Writers Seminar in Ophthalmology, Sep. 16-Sep. 19, 1990 at Universal City, Calif. (the "Koziol Reference"). The Koziol Reference describes the telescopic intraocular lens as a teledioptic lens having a peripheral convex and central concave (minus) portion which have concentric axes. A full range of visual field and normal image size is achieved with the teledioptic lens. A magnified image is obtained when an image in a visual field is viewed through the minus portion of the lens and a high-plus spectacle.